Compressed air switch with auxiliary arc gap



March 30, 1965 K. sPlNNLER COMPRESSED AIR SWITCH WITH AUXILIARY ARC GAP Filed May 18. 1964 FF! A INVENTOR I I I I I I I I I I I l I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I a ATTORNEYS United States Patent O 3,176,104 CMPRESSED AIR SWITCH WITH AUXLIARY ARC GAP Kurt Spinnler, Baden, Aargau, Switzerland, assignor to Aktiengeselisehaft Brown, Boveri & Cie, Baden, Switzerland, a oint-stoclr company Filed May 18, 1964, Ser. No. 368,037 Clainrs Priority, application Switzerland, Sept. 12, wd, 10,306/60 Claims. (Cl. 260-148) This application, which is a continuation-in-part of my prior application Serial No. 137,398, filed September 11, 1961, now abandoned, relates to an improvement in electrical switches operated by compressed air and which are provided with means for connecting a resistance temporarily in parallel between the main load contacts as they are separated in the presence of the compressed air. The circuit for connecting the resistance in and out includes an auxiliary arc gap connected in series with the resistance. Ionized gases arriving at this auxilary spark gap from the quenching Chamber of the main load contacts in conjuncton with the recovery voltage cause the gap to be bridged over by an arc thus placing the resistance -i'n the Circuit to carry current, in parallel to the main load contacts. Additional, fresh compressed air, then arriving at this auxiliary spark gap causes the arc across it to be extinguished thus disconnecting the resistance from the circuit.

With one known construction of compressed air switches, two spaced electrodes having a constant distance therebetween have been provided to establish the auxiliary arc gap. Such a construction has the disadvantage that the same pair of electrodes must be used 'for the ignition of the arc as well as for its quenching. Preferably, a smaller distance between the auxiliary electrodes would be desired for lignition of the arc while a much greater distance would be preferred for the quenching. Hence, a compromise in spacing, as regards fixed electrodes, is usually adopted which, in most cases, is too large for the ignition and too small for the quenching afterwards. The latter has the disadvantage due to a dependency between the characteristic frequency of the alternating current which is to be i'nterrupted by the main contacts of the switch and the recovery voltage during the quenching. At low frequencies, the rise of the recovery voltage curve is less steep than at higher frequencies. Thus. it may occur that a re-striking of the arc between the auxiliary electrodes will easily appear at higher characteristic frequencies as a result of too small a spacing between the electrodes, and these complicate the discounection process. An improvement can be eifected by making one of the electrodes of the auxiliary arc gap movable so as to vary its distance from the other as disclosed in U.S. Patent No. 2,541,792 but this involves increased costs and also can cause difiiculty should the movable electrode develop a tendency to stick.

In order to obtain the greatest possible spacing between the auxiliary electrodes for quenching, but the smallest spacing for ig-niting the arc in the auxiliary spark gap, the invention provides an mproved construction for this gap which comprises not two electrodes but rather three stationary electrodes arranged in such manner that the arc ignites first between a first and a third electrode which have a comparatively small spacing therebetween to i-nsure quick ignition of the arc gap and thus connect the resistance in parallel With the main load contacts. The arc root on the third electrode is then transferred to ICC a second electrode which is spaced a greater distance from the first electrode than is the distance between the first and third electrodes, the arc between the first and second electrodes then being subsequently extinguished to disconnect the resistance.

More particularly, in accordance with the invention the improved three-electrode auxiliary arc gap structure is comprised of a first stationary electrode which is electrically connected with one of the main load contacts of the switch, a second stationary electrode spaced from the first electrode and which is connected to one end of a resistance element, the other end of the resistance element being connected to the other main load contact of the switch, and a third stationary electrode which is electrically connected with the second electrode and extends in a parallel spaced relation with the first electrode and at a distance therefrom smaller than the distance between the first and second electrodes, a part of this third electrode being fashioned in the form of an arcing horn, and the whole arrangement being such that ignition of the arc first takes place between first and third electrodes to temporarily connect the resistance in parallel with the main load contacts of the switch, the roots of the arc migrating along these electrodes until finally the arc root on the third electrode changes over to the second electrode whereupon the arc then burns between the first and second electrodes and the arc between these two electrodes is finally quenched, and the resistance disconnected, by a fresh supply of compressed air which also deionizes the path between the first and third electrodes.

It is thus a basic feature of the improved construction that the spacing between the first and third electrodes is smaller than the distance between the first and second electrodes so that easier ignition of the arc is assured. A greater spacing is established for the arc quenching so that the risk of re-ignition is practically eliminated even under circumstances where the recovery Voltage has a very steep slope. Also, in accordance with the invention, the third electrode is arranged in spaced relation to and paraliels the first electrode, and the end of the third electrode faces in the direction of the incorning ionized gases. Thus, these gases reach the end of the third electrode before they reach the second electrode. Subsequently, the current of fresh compressed air arrives first at the third electrode when the arc root changes over from the third electrode to the second electrode so that a-ny re-sparlcing at this point is likewise prevented.

The foregoing as well as other features of the invention Will become more apparent from the following detailed description of two different embodiments and from the accompanying drawings in which:

EEG. 1 is a view in longitudinal section through one embodiment of the invention wherein the so-called third electrode is configured as a finger with one part thereof extendng parallel to and overlapping the first electrode, and wherein the resistance element is located generally i-nside of the Circuit breaker casing; and

PIG. 2 is also a view in longitudinal section of a second embodiment Wherein the third electrode has the configuraton of a sleeve surrounding a portion of the first electrode, the resistance element being located outside of the circuit breaker casing.

With reference now to FIG. 1 of the drawing, the enclosure and quenching chamber for the auxiliary are gap structure is established within a cylindrical casing 1 preferably made from insulating material. The first electrode of the auxliary arc gap within casing 1 is designated by 53 numeral 2 and is constituted by an elongated stationary pin of conductive material having a rounded nose portion 2a at its outer end, this electrode being located centrally within the casing 1 and parallel with the longitudinal axis thereof. The inner end of electrode 2 is supported by an electrically conductive tubular fitting 3 which is electrically connected with one of the main load contacts of the circuit breaker. In the illustrated embodiment, the fitting 3 is connected with the movable main load contact which is constituted by a stationary contact sleeve 4 and a movable contact sleeve 5 which is slidable on sleeve 4. Contact sleeve 5 terminates in a nozzle plate 6 having a centrally coated. nozzle mouth 7 the periphery of which is engaged by the rounded end of the other main load contact 8 which has the general configuration of a pin and which is supported by a spider 9 of conductive material. A spring 1th surrounds contact sleeve d and bears against the nozzle plate 6 so as to normally niaintain the plate 6' engaged with the main load contact pin 8. Separation of the main load contact members and 8 is eifected by introducing a pressurized gas into the casing 11 surrounding the main load contacts, the gas pushing upward on plate 6 and passing through nozzle 7 into the casing 1 containing the auxiliary arc gap structure.

The second electrode of the auxliary gap structure is constituted by a stationary ring 12 of electricaliy conductive material arranged in a plane perpendicular to the aXis of casing 1 and the center of this ring is located on that axis. Thus, the shortest distance between electrodes 2 and 12 is that indicated by line B extending between a point on ring 12 and a point on the nose portion 2a of electrode 2. The second electrode 12 is secured in its proper position by a plurality of ribs 13 which extend to this ring from anchor points on an electrically conductive apertured plate 14 located with the casing 1. The central portion of plate 14 is connected to one end of the resistance element 15 located within an insulating sleeve 16. The other end of this resistance element is connected to the main load contact pin 8 by an insulated conductor 17 which extends outside of the circuit breaker casing structure.

The third stationary electrode of the auxiliary arc gap structure and which is designated numeral 18 is seen to be constituted asa finger-like member having the configuration of an arcing horn at one portion thereof. One end 18a of the electrode finger 18is secured to one of the ribs 13 and the electrode eXtends in the direction of the first electrode 2 outside of electrode ring 12. It includes an intermediate portion 181) which has an arcuate configuration and the other end portion 180 is essentially rectilinear and extends parallel with electrode pin 2 for a considerable distance and at a distance A from the latter which is less than the distance B between the first and second electrodes 2, 12.

The auxliary arc gap operates in the following manner. When the main load contacts 6, 8 are opened by passing a pressurized gas upwardly through the casing part 1, ionized gases forrned by the arc drawn between these contacts are led upwardly through nozzle '7 into casing part 1 and first reach the end portion 18a of electrode 18 and the adjacent surface of electrode 2 thus to ignite an arc between these two electrodes which serves to connect resistance element 15 in parallel with the main load contacts 6, 8. As a result of the blowing action of the ionized gases on the arc, the latter Will be caused to migrate upward along the surfaces of the electrodes, and the root point of the arc which has been anchored on electrode 18 will now become transferred to electrode ring 12 whereupon the arc continues to burn for a short time between electrodes 2 and 12. Shortly afterward, a blast of fresh compressed air reaches the casing part 1 and this serves to remove any ions remaining in the path between electrodes 2 and 12 and to then quench the auxiliary arc burning between electrodes Z and 12 and thereby disconnect resistance 15 from its paralleling relation with the main load contact. The compressed gas after passing the electrode group 2, 12, 13 fiows upward through apertures 14a in plate 14 and thence out of the casing part 1.

In the modified embodiment of the invention as illustrated in FEG. 2, the third electrode of the electrode group by which the auxiliary arc gap is formed, is a sleeve 19 which includes a lower' cylindrical portion 1% surrounding pin electrode 2, an intermediate portion 1% of increasing diameter and an upper portion 19a which is secured to the ribs 13. The electrode portions liga-1% correspond in function to electrode portions 1811-138 and hence, this embodirnent operates in essentially the same manner as that disclosed in PIG. 1. A further minor structural difference is that the resistance element 15' is located eXteriorly of the casing part 1 within an insulating sleeve 20.

A principal advantage of the iinproved three electrode constructions for the auxiliary arc gap is a greater safety against any re-ignition after disengagernent, and particularly in cases where there is a very steep rise in the recovery voltage and aiso one is assured of a safe and dependable ignition of the arc in the auxiliary arc gap due to the comparatively small electrode spacing which is provided.

I claim:

1. In an electric switch of the type wherein a pressurized gas is utilized to facilitate arc extinct-ion, the combination comprising a main Chamber containing a pair of main load contacts adapted .to be opened and closed in conjunction with the passage lof -pressu-rized gas through said chamber, said contacts when opened drawing a main arc therebetween, a current-reducing resistance element, an auxiliary =arc gap structure operable independently of the arc established between said main load contacts to connect said resistance element in parallel with the entire |main arc drawn between said main load contacts, said `auxiliary arc gap structure being contained within an `auxiliary chamber through which the pressurized gas passes after leaving said main chamber and comprising `a first stationary electrode connected yto 'one of said main load con-tac-ts, a second stati'onary electrode arranged in spaced relation to said first electrode :and which is connected to one end of said resistance element, the other end of said resistance element being 'connected to said other main load contact, and a thirdstationaiy electrode electrically connected to said second electrode and spaced from said first electrode by a distance less than the dis- `tance between said first 'and second electrodes whereupon an auxiliary arc is first ignited between said first and third electrodes to connect said resistance element in parallel wit-h said main arc, and subsequent-ly the .arc root on said' third electrode is transferred to said second electrode and thereafter the arc between said first and second electrodes is quenched to thereby disconnect said resistance element.

2. An electric switch as defined in claim 1 wherein said first electrode of said auxiliary arc gap structure is constituted as :a pin and said third electrode includes a finger-shaped portion extending generally parallel with and overlapping a portion of said first electrode, the free end lof said finger-shaped portion facing 'in the direction of the incoming pressurized gas from said main load contact chamber.

3. An electric switch as defined in clain'l 1 wherein said first electrode of -said auxiliary arc gap structure lis constituted as a pin `and said third electrode includes a cylindric'al portion sur-rounding and lying parallel with a portion of said first electrode -and through which the pressurized gas passes after leaving said main load con- ;tact Chamber.

4. An electric switch as defined in claim 1 wherein said first electrode of said auxiliary 'arc gap structure is constituted as a pin, said second electrode has the configuration of a ring disposed in a plane perpendicular to the axis of said fi-rs-t electrode, and said third electrode includes a finger-shaped portion extending `generally parallel with 'and overlapping a portion of said first electrode,

the free end of said finger-shaped porti-on f'acing -in the direction of the incoming pressurzed gas from said main load contact ohamber.

5. An electric switch as defined in claim 1 wherein said first electrde of said auxiliary are gap structure i's con- |stituted 'as -a pin, said second eleetrode has the configuration of a iing disposed in a piane perpendicular to the axis of said first eiectrode, and said third electrode inciudes a cylind'ricai portion sur-rounding and lying parallel with la portion of said first electrode and through which 1 the pressurized gas passes iafter leaving said main load contact ich-amber.

References Cited in the file of this patent UNITED STATES PATENTS 2,365,132 Amer et al. Dec. 12, 1944 FOREIGN PATENTS 584,718 Great Britain Jan. 21, 1947 607,037 Great Britain Aug. 25, 1948 

1. IN AN ELECTRIC SWITCH OF THE TYPE WHEREIN A PRESSURIZED GAS IS UTILIZED TO FACILITATE ARC EXTINCTION, THE COMBINATION COMPRISING A MAIN CHAMBER CONTAINING A PAIR OF MAIN LOAD CONTACTS ADAPTED TO BE OPENED AND CLOSED IN CONJUNCTION WITH THE PASSAGE OF PRESSURIZED GAS THROUGH SAID CHAMBER, SAID CONTACTS WHEN OPENED DRAWING A MAIN ARC THEREBETWEEN, A CURRENT-REDUCING RESISTANCE ELEMENT, AN AUXILIARY ARC GAP STRUCTURE OPERABLE INDEPENDENTLY OF THE ARC ESTABLISHED BETWEEN SAID MAIN LOAD CONTACTS TO CONNECT SAID RESISTANCE ELEMENT IN PARALLEL WITH THE ENTIRE MAIN ARC DRAWN BETWEEN SAID MAIN LOAD CONTACTS, SAID AUXILIARY ARC GAP STRUCTURE BEING CONTAINED WITHIN AN AUXILIARY CHAMBER THROUGH WHICH THE PRESSURIZED GAS PASSES AFTER LEAVING SAID MAIN CHAMBER AND COMPRISING A FIRST STATIONARY ELECTRODE CONNECTED TO ONE OF SAID MAIN LOAD CONTACTS, A SECOND STATIONARY ELECTRODE ARRANGED IN SPACED RELATION TO SAID FIRST ELECTRODE AND WHICH IS CONNECTED TO ONE END OF SAID RESISTANCE ELEMENT, THE OTHER END OF SAID RESISTANCE ELEMENT BEING CONNECTED TO SAID OTHER MAIN LOAD CONTACT, AND A THIRD STATIONARY ELECTRODE 